Effect of Ca~(2+),Ba~(2+),and Sr~(2+) on Alginate Microbeads

摘要

Microcapsules of alginate cross-linked with divalent ions are the most common system for cell immobilization.In this study,we wanted to characterize the effect of different alginates and cross-linking ions on important microcapsule properties.The dimensional stability and gel strength increased for high-G alginate gels when exchanging the traditional Ca~(2+) ions with Ba~(2+).The use of Ba~(2+) decreased the size of alginate beads and reduced the permeability to immunoglobulin G.Strontium gave gels with characteristics lying between calcium and barium.Interestingly,high-M alginate showed an opposite behavior in combination with barium and strontium as these beads were larger than beads of calcium-alginate and tended to swell more,also resulting in increased permeability.Binding studies revealed that different block structures in the alginate bind the ions to a different extent.More specifically,Ca~(2+) was found to bind to G- and MG-blocks,Ba~(2+) to G- and M-blocks,and Sr~(2+) to G-blocks solely.